Transformer, as far as model railroading is concerned, is an AC device used
to change dangerous 112 volts house current to a safer 18 volts with a much
lower current level.
watts to something closer to 20 or less.
levels and/or isolate circuits.
current is transferred from one wire (primary) to other (secondary)
magnetic core is used to increase the efficiency of this transfer
connections added for flexibility
center tap primary
primary wire has extra connection
twin coil primary for 220 vs. 110 AC input
tapped or split like primary
sometimes series for voltage
sometimes parallel for current
sometimes unequal or multiple for various voltages for other circuits
secondaries electrically isolated inside
possible to have a single primary tapped to provide secondary
but dangerous – no isolation from outside current
dangerous power levels